1. Field of the Invention
The present invention relates to an image forming apparatus, such as a copier, a printer, and a facsimile (FAX) machine.
2. Description of the Related Art
An image forming apparatus including an image carrier, such as a photoreceptor (photosensitive drum) and an intermediate transfer belt, gradually deteriorates in function and enters an abnormal state as a result of following factors. The factors are, for example: frictional wear accompanying normal operations; contamination by a harmful material, such as paper dust, from an external source; increased adhesion and loss of an external additive accompanying excessive stirring of toner as a result of an unexpected operation or the like; and contamination and degradation, as well as an accidental failure, of a cleaning unit and a charging unit. Abnormalities occurring in the image forming apparatus cause deterioration in image quality. Specifically, the abnormalities cause an annoying abnormal image with a vertical streak running along a rotation direction, a blurred image, an abnormal image with a horizontal streak running perpendicular to the rotation direction, an image with a spot-shaped blemish, an image with a “pinhole”, and the like. However, ordinarily, the deterioration of the image quality, such as those described above, is controlled and operation of the image forming apparatus is continued as a result of image formation conditions being modified through image density control, color shifting control, and the like. When the deterioration of the image quality cannot be controlled through the image density control, the color shifting control, or the like, and the abnormal image is formed on a sheet of paper, a user becomes aware of the abnormality in the image forming apparatus. The user repairs the image forming apparatus by, for example, replacing a component such as the photoreceptor.
In this way, in a conventional image forming apparatus, the image forming apparatus is repaired when the deterioration of the image quality cannot be controlled through the image density control, the color shifting control, or the like, and the abnormal image is formed on the sheet of paper. Therefore, the image forming apparatus continues to form the abnormal image from when the abnormality occurs to when the repair is completed. The image forming apparatus cannot form a normal image during this time and, therefore, stops functioning. As a result, the user suffers a large amount of time loss. Furthermore, when the abnormal image is formed, the image is required to be formed again. As a result, resources (toner and paper) are wasted.
Patent applications related to various image forming apparatuses predicting or judging the abnormality, failure, and the like occurring in the image forming apparatus are being filed. For example, Japanese Patent Application Laid-open No. H5-100517 describes a device that measures an electric potential of an electrostatic latent image formed on a photoreceptor surface and predicts photoreceptor life. The electric potential of the electrostatic latent image is device operation control information.
However, a device, such as that described in Japanese Patent Application Laid-open No. H5-100517, that uses a single piece of device operation control information to predict and judge a device failure risks, for example, erroneously judging a temporary abnormal state caused by temperature variation and the like to be an end of device life or the device failure.
Inventors of the present invention are developing an image forming apparatus that can calculate a comprehensive index value taking into account various device operation control information. Based on the calculated comprehensive index value, the image forming apparatus can judge whether the image forming apparatus is in the abnormal state and predict an occurrence of the device failure. The inventors have found from experiments that failures can be predicted and judged with higher accuracy (robustly) and with few erroneous judgments, through the use of judgment and prediction methods such as this.
As a result of keen examination, the inventors have found that information acquired from position detection data includes information useful for the prediction and judgment of device abnormality and the device life. The position detection data is acquired when a detection pattern position detecting unit detects a position of a detection pattern formed on an image carrier
A position detecting sensor used for detecting the position of the detection pattern, such as this, includes a light-emitting element and a light-receiving element. The light-emitting element emits light. The light-receiving element receives diffused reflection light diffused and reflected by a detection pattern image. The position detecting sensor also includes a slit component to accurately determine the position. The slit component has a slit having almost a same width as a line width of the detection pattern. The light-receiving element receives light that has passed through the slit in the slit component.
A detection signal from an ordinary detecting sensor detecting a detection pattern image is broad. On the other hand, a detection signal from the position detecting sensor in the above-described configuration is sharp. Because the position detecting sensor outputs a sharp detection signal, the position detecting sensor can perform highly accurate position detection.
When the toner, the photoreceptor, the charging unit, a developing unit, a transferring unit, and the like deteriorate, the abnormal image is formed in a linear detection pattern image. The abnormal image is, for example, an image with decreased image density, the “pinhole”, or a “wormhole”. When the image density of the detection pattern decreases, the detection signal outputted from the position detecting sensor and serving as the position detection data of the detection pattern becomes broad. As a result, position information acquired based on the position detection data varies. When the charging unit and the photoreceptor deteriorate, the “pinhole” is formed in the linear detection pattern. When the “pinhole” is formed, an output value outputted from the position detecting sensor significantly decreases, and the position information cannot be acquired from the position detection data. When the “wormhole” is formed in the linear detection pattern as a result of the deterioration of the transferring unit, the position detection data acquired by the position detecting sensor has two peaks.
In this way, through keen examination, the inventors have found a correlation between the position detection data acquired by the position detecting sensor and device deterioration. In other words, the inventors have found that the information acquired from the position detection data includes information on the deterioration of the toner, the photoreceptor, the charging unit, the developing unit, the transferring unit, and the like. The information on the deterioration of the toner, the photoreceptor, the charging unit, the developing unit, the transferring unit, and the like is information useful for the prediction and judgment of the device failure and the device life.
Toner is deposited onto an image carrier surface until a transfer position or a photoreceptor cleaning position is reached. Materials added to the toner, such as silica, titanium oxide, and wax, may be deposited onto the image carrier surface. Over time, various contaminants form a film over a photoreceptor surface, depending on usage environment, usage conditions, and the like of the device. As a result, the image carrier deteriorates.
Reflection light reflected by the image carrier surface differs between when scratching or filming occurs on the image carrier surface and when scratching and filming do not occur on the image carrier surface. In other words, the detection data regarding the reflection light reflected by the image carrier surface includes information on the deterioration of the photoreceptor.